Barth syndrome is an X-linked recessive disorder characterised by dilated cardiomyopathy and a variable expression of skeletal myopathy, short statue and neutropenia. Molecular genetic analysis is currently the most reliable diagnostic method. A kindred with a novel 535delC mutation in the G4.5 (TAZ) gene responsible for Barth syndrome is presented. Beside the patient, the same mutation was detected in patient's mother and grandmother. In contrast to the so far reported patients with mutations in the same region of G4.5 (TAZ) gene, the patient described here has only a mild and transitory clinical presentation. This could be attributed to alternative splicing of G4.5 (TAZ) gene, since mRNA lacking exon 6 (with 535delC mutation) was detected. Genetic analysis of the G4.5 (TAZ) gene was helpful for establishing the precise diagnosis of Barth syndrome and for adequate genetic counselling. Predicting the phenotype on the basis of mutations is unreliable especially if mutations are localised in alternatively spliced exons of the G4.5 (TAZ) gene which may result in a milder clinical presentation than expected.